Functional detection in primate brains has particular advantages because of the similarity between non-human primate brain and human brain and the potential for relevance to a wide range of conditions such as stroke and Parkinson's disease. In the proposed research, we use photoacoustic imaging (PAI) to detect functional changes at primary motor cortex of rhesus monkeys. In a rhesus monkey, primary motor cortex is buried in the precentral gyrus, which extends down 8-9 mm below the surface. Therefore, the advantage of PAI for imaging deeper structures is particularly beneficial for this application. In summary, the advantages of utilizing PAI for the detection of primate brain function include: (1) durotomy is not required, therefore, it is a minimal-invasive process;(2) detecting optical absorption properties, which is intrinsically sensitive and provide high contrast;(3) imaging buried cortical structures;(4) high-resolution of ~100 5m;(5) potentially PAI can be performed in real-time. The long term goal of this research is to develop PAI as a qualified tool for high-resolution functional brain imaging in primate research. The objective of current research is to test the feasibility of PAI for detection of primate brain activation using a minimal-invasive procedure. The establishment of a minimal-invasive procedure for research is important because it reduces the stress on the animal while studies can be carried out in a friendly environment to produce highly reliable results. The underlying hypothesis of this proposal is that PAI can reliably detect primary motor cortex activation associated with forelimb movement in rhesus macaques through the dura matter, and provide depth-resolved functional information. The specific aims of this study include (1) to construct a PAI system for monkey brain cortex imaging;(2) to produce both structural and functional images on monkey brain cortex;(3) to compare the sensitivity and resolution of PAI with other established techniques. PUBLIC HEALTH RELEVANCE: In this project, we propose to test the feasibility of photoacoustic imaging technique for brain function imaging in non-human primates. With photoacoustic imaging, buried cortical structures might be imaged with optical contrast at ultrasound resolution. The success of this project will potentially contribute to studies involving stroke and Parkinson's disease in non- human primates.